DE 101 39 050 A1 relates to a method and an apparatus for carrying out an automatic state of charge equalization. In this case, data relating to the driving habits of the vehicle owner are statistically acquired. After detecting the need for a state of charge equalization, these data are used to provide an optimum time for initiating a preparation phase for the state of charge equalization and the subsequent performance phase.
DE 10 2005 023 365 A1 relates to battery management for batteries in hybrid vehicles. A battery variable such as T, SOC, SOH is determined using a mathematical battery model which describes the thermal and/or electrical behavior of a battery. The battery can be used in a particularly effective manner when the future electrical load IBat(t) of the battery (4) is estimated and the battery model calculates the future development of the battery variable Z, SOC, SOH on the basis of the estimated electrical load IBat(t).
The battery of an electrically operated vehicle, a hybrid vehicle or an electric vehicle comprises an arrangement and electrical connection of secondary cells, for example lithium ion battery cells. The battery also usually comprises a control or regulation device which is used to measure the battery cell voltages, the battery cell temperatures and the total current and to use these measurement variables in a model-based manner to predict the maximum electrical powers or currents which may be requested by an electrical drive from the battery in the next time steps. The result is directly transmitted to the drive, for example, via a data bus system, for example a CAN bus.
The electrical drive of a vehicle, more precisely the power electronics, is likewise informed of a desired torque to be set by the vehicle via such a bus system, the origin of which torque is in the gas pedal position and therefore with the driver, for example. The power electronics attempt to provide this desired torque by connecting a B6 semiconductor bridge. The B6 semiconductor bridge is able to apply its input voltage in modulated form to the phases of the electrical machines and to generate a torque by means of the resulting current. The power electronics are intended to comply with the power/current prediction for the battery at any time in order to avoid stressing the battery beyond the permitted degree.
Since the battery and the drive are a physically connected unit, it is entirely possible for the power electronics to request higher powers or currents from the battery than is beneficial to the battery. In this case, the battery has only the theoretical last possibility of opening its main contactors. If the battery does not do this, which will also be impossible in most driving situations for reasons of safety, the following is the effect on the battery, depending on overloading:
More strongly progressive ageing of the battery cells may result. More severe heating of the battery cells can also be feared and, following therefrom, possibly the contravention of safety-critical temperature levels. Finally, voltage limits for the battery cell which are stored in software are contravened.
The extreme situation which would also affect the power electronics would be a low-impedance short circuit applied to the battery via the bridge circuit in the power electronics.